1. Field
The present disclosure relates to redox flow batteries, and more particularly, to redox flow batteries having high energy efficiencies and energy densities.
2. Description of the Related Art
Secondary batteries are highly effective systems for storing energy, and are used in various applications from small mobile phones to medium and large electric power storage systems. Particularly, they are used as major parts in the fields of semiconductors and liquid crystals; acoustics, and communications such as cellular phones and notebooks. Also, they have been recently used as power sources for hybrid automobiles.
Such systems for storing electric power require more stable supplies of energy and high levels of effectiveness in energy conversion. In this context, redox flow batteries have received great attention as secondary cells having high values in power and durability, and suitability for large electric power storage systems.
Contrary to other batteries having solid active substances, redox flow batteries have ions in an aqueous solution as active substances, and are worked by a mechanism in which electric energy is generated and stored by oxidation/reduction reactions of the ions on a cathode and an anode.
In other words, redox flow batteries contain electrolyte solutions (solution) in which active substances for the electrodes are dissolved in solvents. If a battery consisting of a catholyte and an anolyte having different oxidation states is charged, an oxidation reaction is generated on the cathode, and a reduction reaction is generated on the anode. In this case, the electromotive force for the battery is determined by the difference in the standard electrode potentials (E0) of the redox couples constituting the catholyte and the anolyte. The electrolyte may be supplied from an electrolyte tank by a pump. Such batteries have both the advantages of general cells having rapid rates of redox reactions on the surfaces of the cathode and anode, and of fuel cells having high power.